Impact of aortic root geometry on hydrody-namic performance of transcatheter aortic valve prostheses

AbstractAssessment of hydrodynamic performance of transcatheter aortic valve prostheses (TAVP) in vitro is es-sentially in the fields of development and approval of novel implants. For the prediction of clinical performance, in vitro testing of TAVP allows for benchmarking of different devic-es, likewise. In addition to the implant itself, also the testing environment has a crucial influence on leaflet dynamics and quantitative test results like effective orifice area (EOA) or aortic regurgitation.Therefore, within the current study we developed simpli-fied physiological and pathophysiological vessel models of the aortic root as a tool for in vitro hydrodynamic testing of TAVP in idealized and worst case conditions. We used 3D printing and silicone cast molding for manufacturing of aortic root models with variable degree of stenosis. Design of aortic roots with normal, mild and severe stenosis was developed according to Reul et al. For manufacturing of tripartite cast-ing molds, a 3D printer was used. Both outer mold parts and the mold core were manufactured from polylactide filament and water soluble polyvinylalcohol filament, respectively. In vitro hydrodynamic performance testing of an exemplary commercially available TAVP implanted in different aortic root models was conducted according to DIN EN ISO 5840-3:2013, using a pulse duplicator system. Manufactured aortic root models were highly transparent, dimensionally stable and therefore suitable for hydrodynamic testing of TAVP. Both, EOA and regurgitant fraction in-creased with increasing degree of stenosis from 1.6 ± 0.1 cm2 to 1.8 ± 0.1 cm2 and 8.6 ± 6.5% to 20.2 ± 4.2% (n = 30 cy-cles), respectively.We successfully developed a testing environment ena-bling sophisticated evaluation of hydrodynamic performance of TAVR in pathophysiological worst case conditions.

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Impact of aortic annulus geometry according to ISO 5840:2019 (draft) on hydrodynamic performance of transcatheter aortic valve prostheses

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2020-3117 ◽

2020 ◽

Vol 6 (3) ◽

pp. 454-457

Author(s):

Jan Oldenburg ◽

Sebastian Kaule ◽

Stefan Siewert ◽

Klaus-Peter Schmitz ◽

Michael Stiehm ◽

...

Keyword(s):

Aortic Valve ◽

Hydrodynamic Performance ◽

Performance Criteria ◽

Modular System ◽

Effective Orifice Area ◽

In Vitro Test ◽

Transcatheter Aortic Valve ◽

Valve Prostheses ◽

Hydrodynamic Testing

AbstractTo assess the hydrodynamic performance of transcatheter aortic valve prostheses (TAVP), in vitro test using pulse duplicators is required. Test conditions as well as minimum performance criteria are specified in ISO 5840- 3:2013 and ISO 5840-3:2019-draft. In the 2019 published draft, modifications regarding hydrodynamic testing are proposed. Among others, the geometrical configuration of the fixation has changed, with the intention to improve the anatomical representation as well as the comparability of results from different test laboratories. We analyzed the consequences of altered annulus fixations regarding native leaflets as well as a step in the proximal area of the protheses to prevent their migration. The analyses were conducted with regard to the degree of calcification of the annulus ring on hydrodynamic parameters. By using 3D stereolithography printing technology, molds for casting of silicone elastomer of annulus models with and without native leaflets were manufactured. A modular system enabled us to use the same annulus ring to model the degree of calcification as well as different step sizes. We performed in vitro hydrodynamic testing according to ISO 5840-3:2019-draft of a selfexpandable valve prototype with porcine pericardial leaflets by using a commercially available pulse duplicator system. As expected, regurgitation increases with increasing degree of calcification, whereby the use of a step has no influence on the backflow of fluid during diastole. The effective orifice area (EOA) of the valve showed a clear tendency with respect to radial protrusion of the step. The EOA decreased as the radial protrusion increased. We also present a suggestion to prevent migration without affecting the general test results, by using a novel step design. We also found that the novel annulus model with native leaflet drastically reduced the regurgitation.

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Does transcatheter aortic valve alignment matter?

Open Heart ◽

10.1136/openhrt-2019-001132 ◽

2019 ◽

Vol 6 (2) ◽

pp. e001132 ◽

Cited By ~ 1

Author(s):

Jacob Andrew Salmonsmith ◽

Andrea Ducci ◽

Gaetano Burriesci

Keyword(s):

Aortic Valve ◽

Aortic Root ◽

Performance Data ◽

Root Anatomy ◽

Hydrodynamic Performance ◽

Transcatheter Aortic Valve ◽

Flow Stagnation ◽

Image Velocimetry ◽

Valve Function

ObjectiveThis study investigates the effect of transcatheter aortic valve (TAV) angular alignment on the postprocedure haemodynamics. TAV implantation has emerged as an effective alternative to surgery when treating valve dysfunction. However, the benefit of avoiding surgery is paid back by the inability to remove the native diseased leaflets and accurately position the device in relation to the aortic root, and the literature has shown the root anatomy and substitute position can play an essential role on valve function.MethodsA commercial TAV was placed in a silicone mock aortic root in vitro, including mock native leaflets, and either aligned commissure-to-commissure or in maximum misalignment. Haemodynamic performance data at various stroke volumes were measured, and Particle Image Velocimetry analysis was performed at a typical stroke volume for rest conditions. The two configurations were also studied without mock native leaflets, for comparison with previous in vitro studies.ResultsHaemodynamic performance data were similar for all configurations. However, imaging analysis indicated that valve misalignment resulted in the central jet flow not extending to the root wall in the native commissures’ vicinity, replaced by a low shear flow, and a reduction of upper sinus flow of 40%, increasing flow stagnation in the sinus.ConclusionsTAV misalignment did not result in a significant change in valve hydrodynamic performance, but determined some change in the fluid flow patterns, which may promote pathological scenarios, such as increased thrombogenicity of blood flow within the sinuses of Valsalva, and plaque formation around the lumen of the sinotubular junction.

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Aortic regurgitation after transcatheter aortic valve replacement

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2018-0048 ◽

2018 ◽

Vol 4 (1) ◽

pp. 195-198

Keyword(s):

Aortic Valve ◽

Hydrodynamic Performance ◽

In Vitro Test ◽

Valve Prosthesis ◽

Test Setup ◽

Transcatheter Aortic Valve ◽

Implantation Depth ◽

First Results ◽

Valve Prostheses

AbstractThe assessment of hydrodynamic performance of transcatheter aortic valve prostheses in vitro is essential for the develosepment and approval of novel devices. Therefore, this study aims to investigate the correlation of target implantation depth and paravalvular regurgitation in a controlled in vitro test situation. We designed a test setup with retrograde steady flow conditions measuring paravalvular regurgitation as a function of increasing pressure on the closed valve ranging from 0 mmHg to 200 mmHg. Our future aim is to benchmark different valve prosthesis designs and describe the correlation between target implantation depth, paravalvular regurgitation and prosthesis design aspects. The current study describes the developed test setup, validation experiments as well as first results for a selfexpanding valve prosthesis. The highest regurgitation was measured at an implantation depth of 2 mm. In fact, regurgitation increases from 26.1 ± 8.2 ml/min at 0 mmHg to 1,490.7 ± 182.7 ml/min at 160 mmHg. The slightest regurgitation, however, was measured for an implantation depth of 6 mm ranging from 2.2 ± 0.6 ml/min at 0 mmHg to 605.8 ± 18.9 ml/min at 200 mmHg.

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Fluid Study of Transcatheter Aortic Valve Deployment Into Patients With Varying Coronary Ostia Position

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53891 ◽

2011 ◽

Author(s):

Eric Sirois ◽

Qian Wang ◽

Susheel Kodali ◽

Wei Sun

Keyword(s):

Aortic Valve ◽

Aortic Root ◽

Cfd Simulation ◽

Patient Specific ◽

Coronary Ostium ◽

Case Scenario ◽

Element Analysis ◽

Worst Case ◽

Transcatheter Aortic Valve ◽

Coronary Ostia

Recently, minimally-invasive transcatheter aortic valve (TAV) replacement has emerged as a viable alternative to traditional open-chest heart valve replacement for high risk patients who otherwise have limited or no treatment options. Although significant experience with TAV procedures has been gained, various adverse effects have been observed after device implantation [1, 2]. One adverse event is the impairment of coronary artery flow. Because the TAV stent pushes the native leaflets towards the sinus of Valsalva during TAV deployment, the flow boundaries in the aortic root are consequently altered. A worst case scenario would be the occlusion of the coronary ostia. Reduced flow to the coronary arteries has also been observed for some patients following TAV intervention [3]. With IRB approval, we recently conducted a dimensional analysis of 3D aortic root geometries, reconstructed from 64-slice CT scans of 95 patients [4]. TAV-relevant dimensions were measured. The spatial distribution of the left coronary ostium was quantified (Fig. 1). In this study, we will construct a patient-specific aortic root model with varied coronary ostium locations as shown in Fig. 1, and perform a combined finite element analysis (FEA) and computational fluid dynamics (CFD) simulation to investigate hemodynamic environment changes that occur following TAV intervention.

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A Novel Stent for Percutaneous Heart Valve Implantation: First In Vitro Results

Journal of Biomechanical Engineering ◽

10.1115/1.4001026 ◽

2010 ◽

Vol 132 (5) ◽

Cited By ~ 4

Author(s):

C. Marchand ◽

F. Heim ◽

B. Durand

Keyword(s):

Aortic Valve ◽

Valve Replacement ◽

Heart Valve ◽

Aortic Root ◽

Vascular Stents ◽

Valve Prostheses ◽

Percutaneous Heart Valve ◽

Valve Implantation ◽

Surgical Valve Replacement

Percutaneous aortic valve implantation has become an alternative technique to surgical valve replacement in patients with high risk for surgery. This technique is at its beginning and stents used for valve prostheses remain standard vascular stents. These stents are, however, not designed to undergo heart valve stress. They do not match the aortic environment geometry, and induce exaggerated tissue traumatism. Reduced implant lifetime may therefore be expected. The purpose of the present work is to evaluate in vitro the technical feasibility of noninvasive aortic valve replacement with a novel more specific stent. This stent is especially adapted to its implantation environment with a design that matches the shape of the aortic root while respecting the valve functions. We present a design, a manufacturing process and in vitro performances for the stent under static pressure loading and pulsatile flow. The stent shows good dynamic behavior in keeping position imposed at implantation time and in matching the aortic root dimensions changes. Prosthesis static and dynamic regurgitation are evaluated and show values close to those obtained with other commercially available prostheses.

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Influence of leaflet geometry on hydrodynamic performance of transcatheter aortic valve prostheses

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2019-0119 ◽

2019 ◽

Vol 5 (1) ◽

pp. 473-475

Author(s):

Kaule Sebastian ◽

Pfensig Sylvia ◽

Siewert Stefan ◽

Sylvia Pfensig ◽

Stefan Siewert ◽

...

Keyword(s):

Aortic Valve ◽

Material Selection ◽

Aortic Pressure ◽

Hydrodynamic Performance ◽

Closing Volume ◽

Electrospinning Technique ◽

Transcatheter Aortic Valve ◽

A Value ◽

Risk Patients ◽

Valve Prostheses

AbstractThe implantation of transcatheter aortic valve prostheses (TAVP) for therapy of aortic valve stenosis shows more and more clinically non-inferiority results compared to surgical valve replacement in intermediate and low risk patients. Commonly clinically used TAVP are manufactured from chemically fixed xenograft leaflet material, e.g. bovine or porcine pericardium. While the clinical use of TAVP currently extends, challenges concerning valve durability and leaflet calcification have to be addressed. In this regard, artificial leaflet materials represent a promising option for a next generation of TAVP. As a first step for the development of TAVP from polymeric nonwoven, the aim of this study was to determine the influence of leaflet geometry on hydrodynamic performance of TAVP prototypes. Based on a parametric model of the valve leaflets, we varied the curvature of the belly line forming the leaflet coaptation area from an initial, quite concave, leaflet geometry with a value of 0.5° to an almost straight geometry for the leaflets with a value 0.15°. Manufacturing of TAVP prototypes was conducted by means of electrospinning technique with a polycarbonate based silicone elastomer. Hydrodynamic characterization according to ISO 5840-3 standards was performed using a pulse duplicator system with a heart rate of 70 BPM, systolic duration of 35%, mean aortic pressure of 100 mmHg and a stroke volume of 96 ml. Cardiac output as well as mean transaortic pressure gradient, closing volume, leakage volume and regurgitation were measured to compare the different leaflet geometries. To summarize, the curvature of the leaflets’ belly has a crucial impact on TAVP hydrodynamics under physiological test conditions. In particular, the opening and closing behavior is strongly influenced by a steeper curvature leading to larger closing volumes and higher regurgitant fractions. Further studies are planned to identify an optimum with respect to leaflet material selection, leaflet geometry and hydrodynamic properties of TAVP.

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